Dustin Johnson is no rookie when it comes to penalties assessed in the final round of a major. Who can forget his famous bunker episode at the PGA Championship a few years ago? At that time, he merely missed out on a playoff, but the rule was clear and even he himself admitted he'd made a mistake. There is no question he grounded his club and no question he was in a bunker. It was really hard to tell it was a bunker - I know I had no idea - but many people did and it is his job to notice such things.
Fast forward to this year's U.S. Open. He was Dustin again in a rules quandary. Did he in some way cause the ball to move during his practice stroke on the fourth green? This is the question that everyone is interested in answering. Now that the dust has settled a little on this issue we are starting to see that some mistakes were made and many - far more than I thought - professional golfers are not clear on the rules.